1. Field of the Invention
The present invention relates generally to exhaust control systems for internal combustion engines, and more specifically to a sound attenuation device including multiple flow paths therein, for reducing exhaust noise throughout the audio frequency range. The present invention is properly considered an exhaust sound attenuation and control system, as it not only reduces sound levels, but may reduce emission levels as well by means of internal coatings of emissions reduction material which provide catalytic reaction of exhaust pollutants passing through the device.
2. Description of the Related Art
While the internal combustion engine has proven to be a reasonably good power source for motor vehicles, it is not without its drawbacks. One of the chief drawbacks of the internal combustion engine is the noise output which results from the rapid burning of fuel in the combustion chambers of the engine, and the rapid expulsion of the hot exhaust gases into the atmosphere. As a result, legislation in virtually every area of the world requires motor vehicles to have equipment which reduces sound output.
Accordingly, mufflers, resonators and other such sound attenuating devices have been known for many years, since shortly after the very earliest development of the internal combustion engine. These two types of sound control devices, i.e., mufflers and resonators, have generally not been combined into a single unit due to conflicting characteristics and physical requirements.
Mufflers are generally installed near the output end of an exhaust system, where the exhaust gases have cooled somewhat, and are adapted to attenuate the sound level of the exhaust through a wide range of frequencies. Relatively low temperature, mild steels are acceptable for such use, with the primary consideration for durability being corrosion resistance. Mufflers operate by passing the exhaust gases through a series of pipes within the muffler shell, with the pipes generally having a series of smaller passages or orifices in their side walls. The exhaust gases are forced through these side passages by the pressure developed by the operating engine, with the muffler serving to attenuate the exhaust sound through a relatively wide range of frequencies.
Many exhaust systems also incorporate a resonator. Resonators are also sound attenuation devices, but operate on a completely different principle than that of the muffler. The resonator is adapted to pass the exhaust gases therethrough with little or no impedance, while canceling or absorbing sounds within a certain relatively narrow and well defined frequency range. This range is generally relatively high, with the muffler being relied upon for the attenuation of lower exhaust frequencies.
The resonator may be placed either upstream or downstream from the muffler, and is used to quiet any noises not damped by the other components of the exhaust system.
While the present invention is primarily directed to various embodiments of an exhaust sound attenuating device which serves the function of both muffler and resonator in a single unit, the present invention may also include means for treating exhaust emissions as well. By the time of the 1950s, it was becoming apparent that the ever increasing volume of automobile and truck traffic was generating exhaust emissions which were adversely affecting the environment. This was particularly true in urban areas and other areas where geographic and meteorological conditions combined to create areas where such emissions do not readily dissipate. Accordingly,. by the late 1960s, various regulations were being implemented to require equipment to reduce exhaust emissions output from automobiles, particularly in California and other urban areas.
While early emissions control efforts provided some relief, standards have become increasingly strict in order to keep pace with the ever increasing volume of automobile and truck traffic throughout the U.S.A. With the development of the catalytic converter, which uses one or more noble metals such as platinum, rhodium, and/or palladium to produce an oxidizing and/or reducing catalytic reaction with the exhaust products and heat generated by the exhaust, a real breakthrough was achieved in the control of vehicle emissions. An automobile equipped with one or more catalytic converters was capable of meeting most, if not all, of the exhaust emissions standards of the time, and the use of catalytic converters became commonplace on automobiles and light trucks powered by spark ignition engines in the U.S.A. More recently, catalytic converters have been developed which incorporate rare earth elements with the noble-metals to increase the efficiency of the catalytic converter.
Catalytic converters require relatively high heat in order to efficiently perform the catalytic chemical reactions necessary to convert exhaust pollutants into relatively innocuous gases. Accordingly, catalytic converters are conventionally installed as closely as possible to the exhaust manifold of the engine itself, and are customarily constructed of relatively high temperature tolerant materials, e.g., corrosion resistant steel. While the present inventor has developed devices which combine the function of the catalytic converter and resonator in a single device, he knows of no single device which combines the functions of the muffler and resonator in a single unit, and which may also include at least some limited catalytic conversion function as well. Such a device would be desirable, as it would save space beneath the vehicle, would reduce weight, and would likely reduce exhaust backpressure in comparison to a series of separate devices. Manufacturing costs for the production of a single device incorporating all of the functions heretofore provided in a series of separate devices would be reduced as well, as would labor costs during vehicle assembly and repair.
The present invention responds to this need by providing a system which combines the functions of the muffler and the resonator in a single device, and which may also incorporate emissions reduction material in order to perform some relatively limited treatment of the exhaust as it passes through the present sound attenuation device. While the present attenuation device will generally be installed somewhat downstream of the conventional catalytic converter, it may be constructed of materials adapted to resist higher temperatures and may be installed somewhat further upstream in the exhaust system, where more efficient catalytic reactions will occur within the device. The present exhaust sound attenuation and control system may be constructed to have any practicable external configuration as desired, and may be constructed as a single unit or as plural, generally parallel units joined by one or more crossover pipes, as desired.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 4,541,240 issued on Sep. 17, 1985 to John H. Munro, titled xe2x80x9cExhaust System For Internal Combustion Engines,xe2x80x9d describes a device having a series of removable foraminous chambers providing sound attenuation, spark and moisture control, and catalytic emission control. While the function of the Munro device is similar to that of the present system, the Munro device has a different internal configuration with exhaust flow having a straighter path. The present system is considerably more compact.
U.S. Pat. No. 5,014,510 issued on May 14, 1991 to Franz Laimbock, titled xe2x80x9cExhaust System, Particularly For Two-Stroke Cycle Internal Combustion Engines,xe2x80x9d describes an exhaust assembly having a relatively wider expansion area which includes a primary catalytic converter therein. A longitudinal divider is installed upstream of the primary catalytic converter element, with the divider also being coated with catalytically reactive material. It is well known that two stroke cycle exhaust systems are relatively limited in their configurations, as it is critical that the system be tuned so as to assist each exhaust pulse in its passage in order to draw the subsequent pulse or charge from the cylinder, in order to attain optimum efficiency and to preclude overheating of the engine. Accordingly, Laimbock does not provide any internal baffling within his exhaust system in order to attenuate noise levels, as is provided by the present exhaust system.
U.S. Pat. No. 5,206,467 issued on Apr. 27, 1993 to Noboru Nagai et al., titled xe2x80x9cMuffler With A Catalyst,xe2x80x9d describes a relatively small, canister type muffler as used on small two and four stroke engines (e.g., lawnmowers, etc.). The Nagai et al. muffler essentially has four compartments, with a pipe-like first compartment projecting into a second compartment, which communicates with a third compartment which leads to a small fourth compartment with a relatively small exhaust outlet passage. The exhaust gases do not pass longitudinally through a series of elongate passages, as in the present system, and the configuration of the Nagai et al. device cannot provide any resonator effect.
U.S. Pat. No. 5,220,789 issued on Jun. 22, 1993 to James E. Riley et al., titled xe2x80x9cIntegral Unitary Manifold-Muffler-Catalyst Device,xe2x80x9d describes an exhaust manifold and system which is bolted directly to the cylinder head of the engine. While Riley et al. include a conventional catalytic converter element, or xe2x80x9cbrick,xe2x80x9d within their manifold, they fail to include any internal baffling to control the exhaust sound level within their manifold. The only internal passages within their device are formed by the relatively small, straight passages of the catalytic converter element itself, which Riley et al. prefer to be as nearly straight as possible to encourage laminar flow therethrough. In contrast, the present system provides a circuitous exhaust flow path therethrough, to attenuate noise levels optimally. The present device may include catalytic coatings therein, but does not include a flow-through catalytic converter element per se, as in the Riley et al. device.
U.S. Pat. No. 5,388,408 issued on Feb. 14, 1998 to Phillip G. Lawrence, titled xe2x80x9cExhaust System For Internal Combustion Engines,xe2x80x9d describes a dual muffler system, in which the mufflers are teed from a single exhaust line upstream, which is in turn fed by one or more catalytic converters. The mufflers of the Lawrence system are essentially straight through devices having a series of pipes therein of different lengths. Little sound attenuation is achieved by such a system, in comparison to the configuration of the present system. While the Lawrence system discloses dual mufflers, their connection to a single point upstream is unlike the dual exhaust embodiment of the present invention.
U.S. Pat. No. 5,426,269 issued on Jun. 20, 1995 to Wayne M. Wagner et al., titled xe2x80x9cMuffler With Catalytic Converter Arrangement; And Method,xe2x80x9d describes a series of embodiments of a muffler having a conventional catalytic converter element axially disposed therein. The path of the exhaust gas flow may take any of a few different routes, depending upon the specific embodiment of the Wagner et al. device. In at least one embodiment, the flow passes axially through the muffler, from one end to the other. In at least one other embodiment, flow doubles back through the muffler shell to exit radially from a port adjacent the axial inlet. None of the embodiments disclose a multiple path internal configuration corresponding to that of the present device.
U.S. Pat. No. 5,477,014 issued on Dec. 19, 1995 to Stephen R. Dunne et al., titled xe2x80x9cMuffler Device For Internal Combustion Engines,xe2x80x9d describes an otherwise conventional muffler, but having an internal coating of zeolite material for protecting the underlying metal structure from corrosion. The Dunne et al. coating does nothing to catalyze exhaust emissions, but is solely directed to the protection of the metal structure of the muffler. Moreover, the Dunne et al. muffler is conventional, as noted above. Among other conventional features, it includes relatively small diameter internal passages, which have diameters smaller than those of the inlet and outlet pipes. This results in excessive flow restriction, which is avoided in the present exhaust system configuration with its relatively large diameter internal passages. U.S. Pat. No. 5,521,339 issued on May 28, 1996 to Michael S. Despain et al., titled xe2x80x9cCatalyst Muffler System,xe2x80x9d describes a relatively small muffler unit intended for use on a two stroke cycle type engine, e.g., chainsaw, lawnmower, etc. The Despain-et al. muffler passes the exhaust gases back over the catalytic converter element therein, after passing through the catalyst element. No multiple paths for exhaust gases is provided by the Despain et al. muffler, and it is noted that the plural internal passages have a total cross-sectional area or diameter which is considerably less than that of the inlet tube, and the outlet passage also has a cross-sectional area less than that of the inlet tube. Such a design results in relatively high backpressure, unlike the present system with its relatively large internal passages.
U.S. Pat. No. 5,881,554 issued on Mar. 16, 1999 to James Michael Novak et al., titled xe2x80x9cIntegrated Manifold, Muffler, And Catalyst Device,xe2x80x9d describes a relatively large and bulky assembly having a series of individual exhaust tubes within a larger manifold housing. The tubes lead to a catalytic converter element, with the internal manifold volume also communicating with the catalytic element. The tubes are perforated to allow gas flow to pass therefrom to the internal volume of the manifold, whereby the assembly acts as a resonator. However, while Novak et al. state that their device also serves as a muffler, no muffler elements are disclosed within the device. In contrast, the present system provides multiple flow paths as a muffler and resonator.
Finally, U.S. Pat. No. 6,109,026 issued on Aug. 29, 2000 to Egon Karlsson et al. , titled xe2x80x9cMuffler With Catalytic Converter,xe2x80x9d describes a small canister type muffler for use with relatively small two stroke cycle type engines. The Karlsson et al. muffler has a configuration more closely resembling that of the Nagai et al. ""467 and Despain et al. ""339 U.S. Pat.s, than the present exhaust system invention. The points of difference raised in the discussion of the Nagai et al. and Despain et al. mufflers, are seen to apply here as well.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus an exhaust sound attenuation and control system solving the aforementioned problems is desired.
The present invention comprises an exhaust sound attenuation and control system for use with internal combustion engines of any practicable type and configuration. The present exhaust system generally comprises an outer shell containing multiple flow paths therein for exhaust gases, with the flow paths resulting in the canceling of certain frequencies of exhaust noise (i.e., acting as a resonator) and also lowering exhaust noise generally throughout the frequency range (i.e., acting as a muffler). Internal components of the present exhaust system may be coated with emissions reduction material in order to provide some limited catalyzing of exhaust emissions, as well.
The present exhaust system is configured so that the cross-sectional areas of the internal and outlet pipe passages are at least equal to, and are preferably greater than, the cross-sectional area of the inlet pipe. This provides relatively free flowing characteristics for the present system, thus reducing back pressure in the exhaust system and improving the efficiency of operation of the associated engine.
The present exhaust system is relatively compact, particularly in comparison to the separate muffler and resonator systems of the prior art. The compact, integrated configuration of the present system enables it to be installed at virtually any location in the vehicle exhaust system. The present system may be formed of high temperature resistant materials (e.g., corrosion resistant steel, etc.), as required, for installing adjacent to the vehicle engine.
The combining of the functions of previously separate components into a single unit, results in significant savings in manufacturing costs, as well as in savings in time and labor during vehicle manufacture and repair. The compact nature of the present exhaust system invention results in lighter weight than assemblies of the prior art, thus further increasing vehicle efficiency. The present exhaust system may be manufactured in a variety of external configurations, each having essentially the same internal configuration. This allows the present system to be adapted to a wide range of different vehicles. Moreover, the present system may be adapted for use as a single or dual system, with crossover pipes as required. The crossover pipes may comprise a single pipe or a plurality of pipes between two or more exhaust control devices of the present invention, and may connect similar or dissimilar chambers or passages within the different devices, as desired, to enhance the versatility of the system.
Accordingly, it is a principal object of the invention to provide an exhaust control system for an internal combustion engine, which system combines and includes features and functions of a muffler and resonator, and which may also include a catalytic conversion function as well.
It is another object of the invention to provide such an exhaust control system having a plurality of alternative flow passages therethrough, for controlling exhaust sound through a wide range of frequencies.
It is a further object of the invention to provide such an exhaust control system having a free flow configuration, with the cross-sectional area of each internal passage and the outlet passage being at least equal to, and preferably greater than, the cross-sectional area of the inlet passage.
Still another object of the invention is to provide such an exhaust control system which may be constructed in any of a number of different external configurations to fit various installations, and which may be provided in a parallel array of two or more units having crossover pipes therebetween, if so desired.
It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.